Method and apparatus for obtaining position data relating to a probe in the ear canal

ABSTRACT

A method for obtaining position data relating to a probe in the ear canal whereby a probe is inserted into the ear canal, the method further comprising the steps of:—determine the distance from the distal portion of the probe to at least one point of the internal circumferential surface of the ear and/or car canal,—obtaining position data using first transducing means associated with the distal portion of the probe and second transducing means fixed relative to the head of the person, where the first transducing means is transmitting a magnetic field, and the second transducing means are detecting the magnetic field generated by the transmitter. The invention also relates to an apparatus for obtaining position data relating to a probe in the ear canal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method and an apparatus for obtainingposition data relating to a probe in an ear canal.

2. The Prior Art

Obtaining data for mapping an internal surface of an ear and ear canal,for providing a 3-dimensional data or digital model of the internalsurface of the ear and ear canal is useful in producing a shell whichhas the exact shape of the canal. The shell may form the basis for anITE or CIC hearing aid. Also earmoulds or shells for other purposes suchas a hearing protection or for headsets may be produced from the datamodel. The shell can be produced on the basis of the data model indifferent ways, such as by recently developed rapid prototyping methodsor by well-known machining, e.g., in a CNC machining center.

Today hearing aid shells are produced on the basis of an ear impressiontaken by introducing a semi-fluent material into the ear canal, which isleft to cure in the ear. After curing the semi-fluent material becomeselastic and coherent and is pulled out of the ear canal in one piece. Ashell is produced on the basis of this ear impression. Having the earimpression taken is associated with discomfort for the person, and inmany cases the resulting shell does not fit the canal very well.Therefor a method and a device is sought whereby a hearing aid shell maybe produced without the necessity of taking the ear impression.

The advantage of having a data model of the ear canal is that theproduction of the shell can take place at any location, which means thathearing aid manufacturers may produce the shells at a central productionfacility. Uniform quality can then be ensured. Furthers the data modelmay be transmitted either as it is obtained or soon thereafter forevaluation at a production facility. Thereby a data model of the hearingaid, which may be realized based on the dimensions and shape of thecanal, may be generated. The data model of the hearing aid can betransmitted back to the end user for visual evaluation.

In the following documents some of the above problems are addressed, butno satisfactory solutions are presented.

U.S. Pat. No. 5,487,012 discloses a method for computer controlledproduction of an adaptive earpiece comprising at least one part which isindividually matched to the contours of an auditory canal. The methodincludes the steps of tracing the contours of the auditory canal toobtain contour data, digitization of the contour data and storage of thedigitized values, converting the digitized values into amulti-dimensional computer model of the external contours of theadaptive earpiece and producing the earpiece on the basis of thecomputer model. The patent mentions that the tracing of the internalcontours of the ear canal may be performed using ultra sound. Thedocument further discloses a method for tracking the ear canal based onthe use of an ear impression, but such a method would not resolve theproblems relating to the usual way of producing shells as describedabove.

U.S. Pat. No. 5,056,204 discloses a method for producing a hearing aidwhich is worn in the ear. The method includes the steps of initiallytaking measurements of the inner space of the ear up to the eardrum foruse in producing an individual shape of the body member correspondingwith the measurements of the inner space of the ear. It is mentionedthat the measurement is done by means of a laser. How this actuallytakes place is not disclosed.

PCT publication WO 00/34739 discloses a method for manufacture of ahearing aid shell comprising a motor actuated ultrasonic probe used toacquire the shape data of the ear canal, an image processing computer,which also incorporates the driving electronics for the probe, with anedge detection algorithm used to filter the data. Thereby a digitalimage file of the three-dimensional topography of the ear canal isobtained. The ultrasonic probe is combined with a fiber optic probe usedto monitor the position of the probe within the canal. The fiber opticprobe comprises an inner coherent bundle of fibres and an objective lensthat relay the image of the canal to a C.C.D. camera and an outerincoherent bundle of fibres that surround the coherent bundle andpermits the illumination of the canal by an external light source thatis optically coupled to the other end of the incoherent bundle. Theposition of the probe is determined solely by monitoring thedisplacement of the probe in one linear direction. Only the possibilityof monitoring the motor, which is a step-motor is mentioned for thispurpose. The probe is mounted on a stiff rod, and is not capable offollowing the possible bends of the ear canal. This limits the use ofthe probe, as many hearing-impaired people (especially older people),have ear canals with sharp bends.

Various methods and apparatuses for determining the internal propertiesof internal surfaces have been suggested. However, none of these areuseful when it comes to mapping the internal surface of a canal of thehuman body, in order to generate a digital model of the interior wall ofthe canal.

U.S. Pat. No. 5,004,339 discloses an apparatus for determining acharacteristic of the inside surface of a bore comprising:

a guided wave fiber optic element capable of insertion into a bore;

a laser light source for directing light onto the proximal end of saidfiber optic element; means for directing light emanating from the distalend of said fiber optic element onto the inside surface of said bore andfor directing light reflected from the inside surface of said bore ontothe distal end of said fiber optic element; and

photo detector means capable of generating an output signal dependentupon light incident thereon;

means for directing light emanating from the proximal end of said fiberoptic element onto said photo detector means whereby the output signalof said photo detector provides an indication of a characteristic of aninside surface of a bore. The patent further concerns a method fordetermining a characteristic of the inside surface of a bore using theabove apparatus. The method may be employed on a body passage. Obtainingdimensional information concerning a cylindrical surface is mentioned,but not described in detail. Visualization of the bore wall of a sampleis described. The sampled and held output of array video data is fed tothe y and z axis of a storage video display with the x axis comprised bya pickoff of the movement along the bore length. No system forgenerating precise information concerning the position and orientationof the distal end of the fiber optic element is mentioned. The means fordirecting light from the distal end of the optic element onto the insidesurface of the bore may be a mirror surface or a lens such as awide-angle lens. The mirror surface can be designed to focus light on apoint of the bore wall surface which is axially forward of theforwardmost portion of the mirror. This may be used to examine thebottommost portion of a blind bore. The patent does not mention thecombined use of a mirror surface and a lens. Also the use of asemi-transparent mirror intended to direct part of the light to thecircumferential surface and another part of the light to the surfacewhich is axially forward of the mirror is not mentioned.

U.S. Pat. No. 5,469,245 relates to a method and an apparatus formeasuring a three-dimensional position of a surface of a lengthwiseobject such as a pipe having a uniform cross-section from acorresponding two-dimensional observed image of the object surface tomeasure, for example, the size of a defect in the surface. The patentdoes not mention systems to determine the exact location and orientationof a probe, which is inserted into the pipe.

U.S. Pat. No. 5,895,927 relates to a method and apparatus for profilingand dimensionalizing an interior cross-sectional portion of a tubularstructure. The probe utilizes a disc of unfocused light to illuminate across-section of the interior surface and images the illuminatedcross-section from the interior surface to a photo detector array, wherethe image can be evaluated. The photo detector array provides acontinuous video signal, which can be fed to a video monitor and to aframe grabber. The resulting array of numbers can be processed by acomputer program to find those pixels, which represent the illuminatedcross-section, and through this, dimensional (diameter) data may beobtained. The patent does not mention systems for determining theposition and orientation of the probe, in order to gain informationrelating to the length of the tubular structure or relating to possiblebends in the tubular structure.

U.S. Pat. No. 6,073,043 describes a method and apparatus for determiningthe position and orientation of a remote object relative to a referencecoordinate frame. The method and apparatus includes a plurality offield-generating elements for generating electromagnetic fields and adrive for applying signals to the generating elements. The signalsgenerate a plurality of electromagnetic fields that are distinguishablefrom one another. The apparatus comprises a remote sensor having one ormore field-sensing elements for sensing the fields generated and aprocessor for processing the outputs of the sensing element(s) intoremote object position and orientation relative to the generatingelement reference coordinate frame. The position and orientationsolution is based on the exact formulation of the magnetic fieldcoupling. The system can be used for locating the end of a catheter orendoscope, digitizing objects for computer databases, virtual realityand motion tracking.

None of the above documents are concerned with the problem of locatingof a probe inside the ear canal with respect to both displacement androtation in order to gain data relating to the geometry of the internalsurface of the ear and ear canal.

SUMMARY OF THE INVENTION

The object of the invention is to provide a method for obtainingposition data of a probe inside the ear or ear canal in order togenerate geometrical data relating to the internal surface of the earand ear canal. The data are used in order to generate a model of theinternal surface of the ear and ear canal.

This is achieved by a method which uses a magnetic field generated atthe tip of a probe, and magnetic field-sensitive elements located fixedrelative to the ear canal to determine the exact location of a probeinside the ear canal. The probe has means for determining the distanceto the internal surface of the canal wall. Based on the position dataand the distance data, a data model of the geometry of the internalsurface of the ear canal may be obtained. The use of this method ofobtaining the position data is very precise. Further it is possible tomake the measurement noise insensitive. Also, the transmitter of themagnetic field may be made small, so that it may easily be build intothe tip of the probe.

In a preferred embodiment the invention uses light to determine thedistance from the tip of a probe to the internal wall of the ear canal,and based on the position of the probe, this information is used togenerate information about the shape of the canal. By the use of lightto determine the distance between the probe and the surface of thecanal, it is possible to locate foreign objects in the canal such ashair or earwax, and these objects are left out of the data model. Inthis way a more precise model is obtained. Further, the use of lightmakes it possible to obtain very precise data. The inside of the earcanal need not be touched during measurement, and this is important fortwo reasons.

Firstly, because the internal surface of the ear canal is very sensitiveand touching thereof is unpleasant for the person, and secondly, the earcanal may deform when touched, and this might disturb the measureddistance values and thereby corrupt the obtained data model.

In an embodiment of the method distance data are obtained and recordedwhile position data concerning the spatial position and rotation of thedistal portion of the probe are obtained and recorded during movement ofthe probe from a first to a second location. Thereby an operator may mapa larger coherent area of the internal surface of the ear canal in aneasy and straightforward way as the data are recorded duringoperator-controlled motion in the probe.

Preferably, the light sensitive element comprises an array of lightsensitive elements such as CCD elements.

In a further embodiment the probe has a flexible part and is capable ofbending. This has the advantage that the probe is capable of assumingthe shape of the ear canal. This makes it possible to insert and retractthe probe the fill length of the ear canal as the probe continuallyassumes the shape of the ear canal. The ear canal of especially elderlypeople may have sharp bends, and by using the invention, the probe maybe carefully maneuvered past such bends as data are recorded, andwithout making impressions in the tissue of the ear canal, which mightcorrupt the measurements.

Foreign objects such as earwax may corrupt the obtained data. In anembodiment of the invention this is avoided by analyzing the light inorder to recognize such objects. This may be done on the basis of thespectral composition of the light received at the CCD.

Measurements may be performed while moving the probe either towards oraway from the tympanic membrane. In an embodiment according to theinvention, the measurements are performed while moving the probe awayfrom the tympanic membrane. The operator may then place the probe deepin the ear, while taking care that the tympanic membrane is not touched,and then start the measurements and pull the probe gently out of the earwhile taking the measurements. The probe may either be pulled out byhand, or a guiding mechanism may be provided to make sure that the probeis moved at a uniform speed.

A further object of the invention is to provide an apparatus forobtaining position data of a probe inside the ear canal of the humanbody in order to be able to generate an exact model of the internalsurface of the ear and ear canal.

A very simple apparatus for obtaining position data is achieved by theapparatus comprising:

-   -   a probe with a distal and a proximal part, whereby the distal        part is intended for insertion into the ear canal, and has means        for determining the distance from the probe to the internal        surface of the ear and/or ear canal,    -   means for obtaining position data regarding the probe by        transmitting means associated with the distal portion of the        probe, and receiving means arranged at fixed positions outside        the canal, where the transmitting means comprise a magnetic        field generating coil, and the receiving means comprise magnetic        sensitive elements such as Hall-elements.

This apparatus ensures precise and reliable position data.

Preferably, the apparatus further comprises a probe having:

-   -   a rod at least one light guide and a light source at the        proximal end of the light guide,    -   a light emitting distal portion insertable into the ear canal        and having means for directing light from the distal end of the        light guide onto at least one point of an internal        circumferential surface area of the ear and/or ear canal,    -   means for receiving the light reflected from the illuminated        area, and means for directing the received light to at least one        light sensitive element to generate an output,    -   means for analyzing the output to determine the distance from        the probe to the internal surface of the canal at points of the        circumference.

Precise distance data is obtainable with this apparatus.

Focusing means in the form of a lens may be inserted in the light pathbetween the light guides and the mirror, to obtain a focused light beamdirected towards the internal canal surface.

Preferably the light sensitive element in the apparatus comprises anarray of light sensitive elements such as CCD elements.

In an advantageous embodiment the light path between the second mirrorsurface and the CCD element comprises an image guide between the distalend and the proximal end of the probe, and the CCD element is arrangedat the proximal end of the probe and receives the light emitting fromthe image guide. A flexible image guide is chosen so that it may bendalong with the probe to follow the bends of the ear canal. The CCDelement is arranged at the proximal end of the image guide, away fromthe ear of the person during measurement. The advantage is here that nosevere space restrictions exist, and the most suitable CCD element maybe chosen along with possible lenses, without regard to size.

In an advantageous embodiment the light source generates lightcontaining wavelengths within a first wavelength range and a secondwavelength range, and at least the first mirror surface is arranged on atransparent body, whereby the mirror surface reflects light in a firstwavelength range and is transparent to light in a second wavelengthrange and transmits the light in the second wavelength range and wherebythe light in the second wavelength range is directed to the area infront of the distal portion of the probe, and the light reflected fromany objects in this area is directed through the transparent body andguided towards the CCD element. By this arrangement it becomes possibleto receive two images at the CCD element, one of the circumference ofthe ear canal, and one of the environment in front of the tip of theprobe. The two images will be in each their wavelength range and maythen be captured by one and the same CCD element.

The mirror surface preferably comprises a coating on the transparentbody.

Preferably, the CCD element is sensitive to light in both the first andthe second wavelength range and the first or second sensitive wavelengthrange may be selected. Thereby one and the same CCD element may be usedto capture pictures from the circumference and from the front of theprobe.

Control of the light received at the CCD may be achieved by controllingthe light input to the light guide. When the area in front of the probeis to be illuminated, light in the second wavelength range is inputtedto the light guide, and when the circumference is to be illuminated,light in the first wavelength is used. Control of the light input to thelight guide may be obtained through control of the light source or bythe use of filters.

In another embodiment the probe comprises two CCD elements sensitive toeach their wavelength range, whereby a mirror having a semitransparentcoating is arranged such that one of the CCD elements receives the lightfrom the circumference and the other CCD element receives the lightreflected from the area in front of the distal portion of the probe. Inthis case the two pictures are available at all times at the two CCDelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a the distal end of a probe showing thelight path for determining the distance to the inside wall of a canal,

FIG. 1A shows a detail of FIG. 1,

FIG. 2 is a sectional view of the probe of FIG. 1 showing the light pathfor determining the distance to an object in front of the distal portionof the probe, and

FIG. 3 is a side view showing the human ear and the arrangement of theposition sensors.

DESCRIPTION OF A PREFERRED EMBODIMENT

The probe shown in FIG. 1 has a distal light emitting portion and a rodportion 9, which connects the distal portion to a proximal part (notshown). The rod portion 9 comprises a flexible pipe 8 and a set of lightguides 3 and an image guide 1. The image guide 1 is placed centrally inthe pipe 8, and the light guides 3 are arranged between the pipe 8 andthe image guide 1. Near the tip of the probe the light guides 3 arefastened between an inner bushing 2 and an outer tube 6. An annular lens4B is arranged at the bushing 2 to capture the light emitting from thelight guides 3, in order to focus said light. The focused light beam isdirected to a first portion of a mirror 5 mounted at the tip of the tube6. The first portion of the mirror 5 has a circumferential conical planewith a top angle of 45°. Thereby the focused light beam emitted from thelens 4B will be directed in a right angel away from the longitudinalaxis of the probe, and towards the surrounding canal wall 11. The tipportion of the tube 6 is made of a transparent material, so that thelight may be transmitted freely through the tube wall.

In FIG. 1 the wall 11 is shown as an example in a first distance at 11Anear the tip of the probe and in a second distance 11B farther away fromthe tip of the probe. Light reflected from the wall at 11A of the canalwill enter the tube 6 and be reflected from a second portion of themirror 5 and enter a second lens 4A. From the lens 4A the light isdirected towards the surface of the image guide 1. If light is reflectedfrom a wall part 11B farther away from the probe, it will also bedirected towards the surface of the image guide 1, but as can be seen inthe enlarged section labeled “5×” this light enters the image guide 1closer to the center thereof. The second portion of the mirror 5 has acircumferential conical plane, but with a top angle which may differfrom 45°.

The image received on the surface of the image guide 1 is transmittedthrough the image guide 1, and will appear at the other end thereof.Here the image is captured by a CCD array (not shown). The signal fromthe CCD is transferred to a signal processing unit for furtherprocessing in order to calculate the distance from the probe to thecanal wall. This is done by a triangulation method well known in theart.

Instead of an image guide, it is possible to arrange the CCD array atthe distal end of the probe, such that the reflected light is capturedat the distal end of the probe. This is a simpler construction, but itrequires a CCD element, which is small enough to be mounted at the tipof the probe, which is going to enter the ear canal. The signal from theCCD element in this case is carried in the usual way by wire back to theproximal end of the probe to be analyzed as described to determine thedistance to the wall of the ear canal.

In the preferred embodiment a focused light beam is directed towards thewall of the canal, but also unfocused light may be used. The advantageof using focused light is that the focused light provides bettercontrast and this result in a more precise detection of the distancebetween the probe and the canal wall.

A single light guide may be used for both directing light to the tip ofthe probe and for transmitting the reflected light back to the CCDelement. But this requires a beamsplitter, and has the disadvantage of areduced signal to noise ratio, and therefore the separate light guidesare preferred.

In FIG. 2 the light path is shown in a second mode of operation of theprobe. The mirror surface 5 is coated with a coating, which in a firstwavelength range reflects all light, but which in a second wavelengthrange transmits all light. The light path of the light in the secondwavelength range is shown in FIG. 2. Here light in the second wavelengthrange emitted from the lens 4B passes through the lens 5 and isreflected from any object 12A, 12B in front of the probe. At 12A and 12Bthe end wall of the canal is shown at two different distances from theprobe. When an ear canal is scanned the tympanic membrane is the end ofthe canal. The reflected light is also transmitted right through mirrorelement 5 and through lens 4A and forms an image of the area in front ofthe probe on the surface of image guide 1. At the proximal end of theimage guide the two pictures, namely the front and the circumferentialpicture, are either led to each their CCD element by the use of afurther semitransparent mirror, or led to one and the same CCD elementwhich is chosen so as to be selectively sensitive to the two wavelengthranges.

Using a colour sensitive CCD element has the further advantage thatcolour information may be used when analyzing the light reflected fromthe surface of an ear canal. If white light is used, it is possible todetermine the relative content of red, green and blue light in thereceived signal, and thereby foreign objects such as earwax may beidentified. This is because earwax will reflect the light in otherwavelength ranges than the naked skin of the ear canal. If thesemitransparent mirror option described above is employed this willcause some restrictions as to how detailed the colour information is, asonly a limited range of wavelengths may be reflected from the mirrorsurface 5. In the generated data model any lump of earwax may be leftout, and the data for the particular surface of the ear canal may begenerated through extrapolation using the data from the surrounding wallparts.

The semitransparent mirror surface 5 provides another possibility,namely that a conventional picture is captured through this mirror. Thisis done by using the image guide in the same fashion as in usualendoscobes. Here light in the wavelength range in which the mirrorsurface is transparent is guided through the image guide from theproximal end thereof to the tip of the probe. Reflected light istransmitted back through the image guide and by means of a beamsplitterdirected towards the surface of a CCD. Thereby the CCD may capture anatural image of the objects in front of the probe, and such an imagecould be valuable for the person conducting an ear scan.

In FIGS. 1 and 2 a coil 7 is shown at the tip of the probe. The coil isused to generate a magnetic field, which is picked up by sensors shownschematically in FIG. 3. At each sensor position A, B and C two ore moresensors are located, which are designed to register the magnetic fieldin each their direction. Through this arrangement the exact location andorientation of the tip of the probe can be determined at any time. Inthe case shown in FIG. 3, the probe is located inside the canal of ahuman ear, shown schematically in the figure. The three sensor locationsare arranged in a fixed construction, which in use is held immobilizedrelative to the person's head. In the embodiment shown in FIG. 3, thefixed construction comprises a tripod, whereby each of the sensorpositions are placed at the outer end of each of the branches of thetripod. In use the coil 7 at the probe tip is driven at a fixedfrequency and by using a lock-in procedure, any noise coming from othermagnetic fields in the surroundings may be cancelled out from the sensorsignals.

In the described embodiment only one coil is located at the tip of theprobe, and the coil is aligned with the length axis of the probe. Thismeans that rotational movement of the probe about its length axis cannotbe detected by measuring the magnetic field. It is suggested accordingto the invention, that the probe is made rotationally rigid, so that ifthe proximal end of the probe is retained and prevented from rotationabout the length axis, then the distal end cannot rotate either. In thisway only three different position and two different rotationalparameters must be obtained to fully locate the probe in the canal.

A guiding arrangement for the probe may be located at the tripod shownin FIG. 3. A guiding arrangement may comprise two or more opposite flatrollers between which the probe is to pass. By slightly squeezing theprobe between the rollers, rotational movement of the probe around thelength direction is prevented. Such a guiding mechanism may however beimplemented in many different ways.

In use, the probe is gently inserted into the ear and the magneticsensors are placed in close relation to the person's head. Placing theprobe in the ear is done while objects in front of the probe aremonitored as described through the semi-transparent mirror. A realpicture may be obtained and/or the distance to the tympanic membrane ismeasured as previously described. The picture captured this way isdisplayed on a monitor, so that the operator may know when the probe isapproaching the tympanic membrane. Once the region near the tympanicmembrane is reached, the measurements may commence. This is done whileretracting the probe as corresponding values of the distances to thecanal wall and the position of the probe are recorded. The recording iscontinued until the probe reaches the outer regions of the outer ear.

1. A method for generating a 3D data model of an inside surface of aperson's ear canal comprising the steps of: inserting a probe into theear canal: determining a distance from a distal portion of the probe toat least one point of an internal circumferential surface of the earand/or ear canal, obtaining data concerning the position and rotation ofthe distal portion of the probe relative to the person's head duringmovement of the probe from a first to a second location using firsttransducing means associated with the distal portion of the probe andsecond transducing means arranged in a fixed construction heldimmobilized relative to the person's head, where the first transducingmeans transmits a magnetic field, and the second transducing meansdetects the magnetic field generated by the first transducing means, andrecording corresponding values of said distances from a distal portionof the probe to points of an internal circumferential surface and theposition of the probe.
 2. A method as claimed in claim 1, where thedistance from the distal portion of the probe to the at least one pointof the internal circumferential surface of the ear and/or ear canal isgained by: inserting a light emitting distal portion of a probe into theear canal and directing light from the distal portion of the probe toilluminate at least one point of the internal circumferential surface ofthe ear and/or ear canal, receiving the light reflected from theilluminated surface, directing the received light to at least one lightsensitive element to generate an output, and analyzing the output todetermine the distance from the probe to the internal surface of the earand/or ear canal at points of the circumference.
 3. A method as claimedin claim 2, where the at least one light sensitive element comprises anarray of light sensitive elements such as CCD elements.
 4. A method asclaimed in claim 3, where the probe has a flexible part and is capableof bending in correspondence to the bends of the ear canal during themovement of the probe from the first to the second location.
 5. A methodas claimed in claim 2, where the light received at the CCD is analyzedin order to identify foreign objects such as earwax.
 6. A method asclaimed in claim 2, where the probe is initially inserted to a positionadjacent the person's tympanic membrane and where the geometrical dataare obtained during extraction of the probe from the ear canal.
 7. Anapparatus for obtaining position data relating to a probe in an earcanal in a person's head, the apparatus comprising, a probe with adistal and a proximal part, whereby the distal part is intended forinsertion into the ear canal and has means for determining the distancefrom the probe to an internal surface of the ear and/or ear canal, meansfor obtaining position data regarding the probe by includingtransmitting means associated with the distal portion of the probe, andreceiving means arranged in a fixed construction and held immobilizedrelative to the person's head at fixed positions outside the canal,where the transmitting means comprise a magnetic field-generating coiland the receiving means comprise magnetic sensitive elements such asHall-elements.
 8. An apparatus as claimed in claim 7, where theapparatus comprises a probe having: a rod at least one light guide and alight source at the proximal end of the light guide, a light emittingdistal portion insertable into the ear canal and having means fordirecting light from the distal end of the light guide onto at least onepoint of an internal circumferential surface area of the ear and/or earcanal, means for receiving the light reflected from the illuminatedarea, and means for directing the received light to at least one lightsensitive element to generate an output, and means for analyzing theoutput to determine the distance from the probe to the internal surfaceof the canal at points of the circumference.
 9. An apparatus as claimedin claim 8, wherein the apparatus is constructed to obtain and retrievedistance data during motion of the probe from a first location to asecond location and where the apparatus comprises means for obtainingposition data concerning the spatial position and rotation of the distalend of the probe during the motion of the probe from the first locationof the second location.
 10. An apparatus as claimed in claim 8, whereinmeans are provided for generating a data model of the internal surfaceof the canal on the basis of the retrieved position and distance data.11. An apparatus as claimed in claim 8, wherein the light sensitiveelement comprises an array of light sensitive elements such as CCDelements.
 12. An apparatus as claimed in claim 11, wherein the lightsource has a wavelength range and the CCD has a sensitivity range suchthat foreign objects such as earwax in the ear canal may be detected andidentified.
 13. An apparatus as claimed in claim 11, where the probecomprise first light guides for transmitting light from the proximal tothe distal end an first mirror surface for directing the light onto theinternal circumferential surface of the canal and a second mirrorsurface for directing the light reflected from the circumferentialsurface of the canal towards the CCD element.
 14. An apparatus asclaimed in claim 11, where the light path between the second mirrorsurface and the CCD further comprise an image guide between the distalend and the proximal end of the probe, and where the CCD element isarranged at the proximal end of the probe, so as to receive the lightemitting from the image guide.
 15. An apparatus as claimed in claim 11,where the light source generates light containing wavelengths within afirst wavelength range and a second wavelength range, and where at leastthe first mirror surface is arranged on a transparent body, whereby themirror surface reflects light in the first wavelength range and istransparent to light in the second wavelength range and transmits thelight in the second wavelength range and where the light in the secondwavelength range is directed to the area in front of the distal portionof the probe, and where light reflected from any objects in this area isdirected through the transparent body and guided towards the CCDelement.
 16. An apparatus as claimed in claim 15, where the CCD elementis sensitive to light in both the first and the second wavelength rangeand where the first or the second sensitive wavelength range may beselected.
 17. An apparatus as claimed in claim 15, where the probecomprises two CCD elements sensitive to each their wavelength range,whereby a second mirror having a semitransparent coating is arrangedsuch that one of the CCD elements receives the light from thecircumference and the other of the CCD elements receives the lightreflected from the area in front of the distal portion of the probe. 18.An apparatus as claimed in claim 8, wherein the fixed constructioncomprises a tripod having branches and wherein the sensors are placed atouter ends of said branches.